If you want to find out if your language is already present in QGIS or who is
currently working on your language you have to take a look in the
Help -> About -> Translators Box in the QGIS Desktop
Application.

You will also find the progress of the translation there (but remember in
every “stable” version it will always stay at the same level).
For finding the current percentage of translation you will either have to
install the nightly build of QGIS or checkout the source code of QGIS and
start translating there.

If you plan to contribute to an existing language or you want to translate
the QGIS GUI into a not yet existing language and for any other related
questions, please contact the Translation Team Leader
(see Organigram) or subscribe with the
qgis-gui-translation-team
mailing list.

After subscribing to the mailing list you are able to send a mail directly to
qgis-tr@lists.osgeo.org asking for help.

We strongly encourage anyone dealing with translations to join this list and
promise that it is usually a very low traffic mailing list.

The QGIS project is always looking for people who are willing to invest some
more time translating QGIS into a foreign language - even perhaps to
coordinate the translation effort.

We are trying to improve our project management process and spread the load
more evenly between people who each have a specific area of responsibility,
so any contribution you have to make will be greatly appreciated.

If you would like to nominate yourself as a coordinator for a new language
please go ahead.
If more than one person nominate themselves as coordinator for the same
language, please contact each other and resolve how you will manage your
efforts.

Please contact the Community Assistant or the GUI
translation team leader to see you name entered in the About Box of QGIS.

The QGIS interface is natively programmed in English. However, it is designed
to be translated into any language quite easily. At this moment over fifty
other languages are already available (though not all well maintained).

All available languages are listed in the QGIS About dialog. It also shows
how much of it has been translated yet. The entire interface contains over
ten thousand pieces of text and a complete translation will take days if not
weeks to be finished. Besides that, the rapid development of the application
continuously causes new and edited texts to be translated. A huge effort and
your help will be appreciated!

The web-based translating platform Transifex is used for all QGIS
translations; the desktop application itself (or GUI), the documentation and
the web site. So the first thing you need is an account to login and get
started.

With requesting a new language please bear in mind that we try to make it as simple
as possible. Just ask for the language you want to translate (regardless in which
country you reside). Only if there are notable differences in the languages (for
example portuguese in Portugal in Brazil) we will create its own version.